Science

How a fungus grows inside a bug, goes on to kill and feed on it

Walking dead: The fruiting body sprouts out from between the insect’s thorax and head, and the fungus takes its nutrition.

Walking dead: The fruiting body sprouts out from between the insect’s thorax and head, and the fungus takes its nutrition.  

When you are an Ophiocordyceps fungus, your life is straight out of a sci-fi movie: Infect a bug, eat from inside, kill it, sprout out and target the next bug. Researchers have now found this fungi (Ophicordyceps nutans) for the first time in central India and show how it infects a stink bug. They also explore the potential of using these fungi as biopesticide and medicine.

It was early summer in 2018 when a team from Pandit Ravishankar Shukla University in Raipur set out on a plant survey at the picturesque Kanger Valley National Park in Chhattisgarh. “By chance we stumbled upon the fungus and dead bug and wanted to study it further. Morphological studies showed that it was Ophicordyceps nutans which has been reported in India only from the Western Ghats,” says Jai Shankar Paul, from the University’s School of Studies in Bio-Technolog, the first author of the paper published in the Proceedings of the Zoological Society.

The fungus was found on its specific host insect Halyomorpha halys. Also called the stink bug, this insect is a pest to forest trees and agricultural crops. The simple but scary modus operandi of the fungi involves infecting the insect when alive, developing fungal mycelium inside its thorax, and when it is time for the spores to come out, kill the bug.

The fruiting body sprouts out from between the insect’s thorax and head, and it continues to take nutrition from the dead body. The fungi are very host-specific, so the spores travel and infect many more stink bugs.

Dr. Paul adds that more studies are needed to understand in detail about the behaviour, mode of action, and exact interaction of the fungus with the insect.

Previous studies have shown that these fungi can be used as a biological pest control agent. The stink bug is known to damage the flower and fruits of soybean, green beans, apple, pear, and the team write that exploring these fungi as a pesticide will help reduce the harmful effect of chemicals in our fields.

“The more interesting and important point to note is that several species of the Ophiocordyceps fungi have medicinal properties. Reports have shown that China has been traditionally using it. Also, in the Western Ghats, the local people use these fungi as an immune stimulator,” adds corresponding author Professor S.K. Jadhav.

The authors say that studies from across the globe have noted that these fungi is rich in biologically active metabolites, vitamin C, phenolic compounds, and also has anti-inflammatory and antioxidant properties.

They also claim that it contains a component called ‘cordycepin’ which has anticancer properties. The fungi can be grown in mass in lab settings and explored further, says the team.

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Printable version | Oct 1, 2020 6:13:29 AM | https://www.thehindu.com/sci-tech/science/how-a-fungus-grows-inside-a-bug-goes-on-to-kill-and-feed-on-it/article31989517.ece

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